Recovering potassium from brines



Patented Aug. 28, 1923.

UNITED sTATss CLINTON E. DQLBEAR, OF SAN FRANCISCO, CALIFORNIA, ASSIGNGR T INDUSTRIAL RESEARCH 00., OF SAN FRANCISCO, CALIFORNIA.

RECOVERING POTASSIUM FROM BRINES.

No Drawing.

To 171 'H'IIOIIL it may cmmern:

Be it known that, I CLINTUN E. Donnmn,

a citizen of the United States, residing at the city and county of San Francisco and State of California, have invented certain new and useful Improvements in Recovering Potassium from Brines, of which the following is a specification.

My invention relates'to the recovery of potassium.

Its object; is to cause the precipitation of potassium and other valuable salts from brines containing a mixture of potassium and sodium salts.

'The principle involved is based upon the fact. that certain salts ot'potassium and sodium are quite insoluble in ammoniaeal solution.

l have found that it ammonia is dissolved in such a brine as occurs at Searles Borax Lake, or at Deep Springs Valley,"( alitornia sodium sulphate, chiefly. is at l'irst precipitated. As the. solution beeouies stronger with ammonia, sodium carbonate and potassium sulphate together with more sodium sulphate precipitate. 'hen the. ammonia absorbed by the brine amounts to a little over ot' the weight; of the. original brine. approximately all of the carbonates and sulphates and over 90% of the borates contained in the original brine are preeipita'ted there't'rom, there remaining still in solution chlorides of sodium and potassium, together with a small quantity of borax.

l have also l'ound that ii' the ammonia is added to the brine rapidly, almost. no potassium salt is precipitated. while it the ammonia is added very slowly, the potassium is more completely precipitated.

it appears that. the. reason for this behavior is that the potassium exists in the brine as potassium chloride and that in order to become insoluble in the ammoniaeal brine. it must. react with the sodium sul- 4 phate present. to form potassium sulphate and sodium chloride, and that For some ob scure reason, this reaction is slow, so that the sodium sulphate preeipitates out, and

r settles from the body of the brine bet'ore sullieieuttime elapses to allow of much potassium sulphate to form.

I have found that if the brine is so agitated that the precipitated sodium sulphate is kept suspended in the brine, durin the lit) Application filed July 17, 1922. Serial No. 575,655.

ammoniacal treatment. tlun the reaction between the sodium sulphate and the potassium chloride proceeds to completion, and a large percentage ot thepotassium is precipitated as the'sulphate. i

In practice, I pass ammonia gas into the brine, keeping: the brine in agitation, until the desired percentage of the potassium therein is precipitated. The amount of ammonia required appears to be somewhat dependent on the composition of the brine and varies say, for example between tour: teen and eighteen per cent; of, the weight of the original brine. when about eihteen per cent of ammonia has been added,the solubilit-ies of the sodium carbonate, sodium sulphate and borax begin rapidlv to decrease and when, say, 22% of ammonia is present, there has been precipitated all but a trace of both carbonate and sulphate. and all but about 0.05% of borax. 'lhese salts can he precipitated all tOgttl'ltl' and afterward refined one from the other by well known methods, or the potassium sulphate mixed with some sodium sulphate and carbonate can be separated from the brine at. a lower degree of saturation with ammonia. and the remainingearbom'ite, sulphate and borate of soda in the brine afterward precipitated by addition of more ammonia. and thus a partial separation of the. salts efi'ected.

After the separation of the. precipitated salts from the ammoniaeal brine, I recover the ammonia from the brine by anv of the well known methods and use this same ammonia again and again, to effect precipitation ol the salts from more brine. Thus the precipitating agent. is used over and over and with very small loss of ammonia.

The great advantage of this method of recovery of potassium and other salts trout brine is the very small cost of operation, since evaporating, .ot' the brine with its attendant di'tiieulties and cost. is eliminated. The cost per unit. of potassium salt recovered is but a fraction of the cost of recovery by evaporation.

I claim 1. The method of recovering potassium from a potassium bearing brine, comprising adding ammonia to the brine, and keeping the first precipitated salt in suspension in the brine, until the potassium is precipitated.

2. The method of reeoverm iotassuun E3 messes form an insoluble preeipita-table potassium salt.

4, The method of recovering potassium from brines containing sodium sulphate and potassium chloride, comprising the precipitation of the sodium sulphate by the addition to the brine of ammonia, and during the ammoniacal treatment keeping the precipitated sodium sulphate in suspension throughout the body of the brine, until the potassium chloride reacts with said suspended sodium sulphate to form potassium sulphate and sodiums chloride.

5. The method of recovering potassium from brines containingpotassium'and sodium salts, comprising the precipitation of the sodium salt by the addition to the brine of amnionia and during the ammoniacal treatment keeping the brine in a state of agitation to n'iaintain the precipitated sodium salt in suspension therein, until by reaction with said suspended sodium salt, the potassium salt in the brine is converted into an insoluble precipitatable potassium salt. 7 s 6; The method of recoyering potassiun from brines containing sodium sulphate and potassium chloride, comprising the precipitation of the sodium sulphate by the addition to the brine of ammonia, and during the ammoniacal treatment keeping the brine in a-state of agitation to maintain the precipitated sodium sulphate in suspension therein, until by reaction with saidsodium sulphate the potassium chloride is converted into potassium sulphate.

In testimony whereof ll have signed my name to this specification,

CLENTON E. DOLBEAR. 

